Ramachandra H. Balundgi

A Review on Biodegradable Plastics

Abstract The interaction between synthetic polymers and the natural environment in terms of the effects of oxygen, radiant energy, and living organisms has been extensively studied over the past two decades [1]. However, the recent trends in the preservation of the environment have created much public interest. This is due to the heavy usage of plastics as packaging materials in consumer industry. Materials used as packaging films and the like are not expected to have a long service life. Among several such materials, polyolefins have received special criticism because of their longevity and stability under soil burial conditions. The most likely degradative processes acting on buried polyolefins are simple oxidation and microbial attack, in addition to photodegmdation under the influence of UV sunlight. The disposal of plastics as refuse or litter is thus a volume problem rather than a weight problem. The relative proportion of plastics in refuse increases every day on account of their low degradability....

A review of polymeric geosynthetics used in hazardous waste facilities

Abstract The generation of hazardous wastes from various sources including chemical industries, hospitals, households, etc., is a worldwide problem and is particularly acute in the United States. The petrochemical and refinery industries produce about 70% of this waste. Geographically, the greatest production of hazardous wastes is known to occur along the United State Gulf coast. Presently, it is estimated that about 80% of the total waste remains toxic for years or even centuries. Inappropriate disposal of these wastes on land creates the risk of contaminating ground water and vegetation causing adverse health effects. This review addresses the geotechnical aspects of the problems related to the management of hazardous waste by the use of polymeric materials as ‘barriers’. Important findings of research efforts on this topic from 1980 through mid-1994 are discussed. The review gives an awareness to the general public and addresses points of interest to field engineers and technologists for the proper handling of wastes by the use of the polymeric geosynthetics acting as membranes or barriers.

Sorption kinetics and diffusion of alkanes into tetrafluoroethylene/propylene copolymer membranes

Sorption kinetics and diffusion of hexane, heptane, octane, nonane, decane, cyclohexane, and 2,2,4-trimethylpentane through tetrafluoroethylene/propylene copolymer membranes were studied using the gravimetric sorption method at 30, 45, and 60°C. Coefficients of diffusion were calculated from Ficks equation. From these data, the permeability coefficients were obtained. Analytical solutions of Ficks relations were used to estimate the liquid concentration profiles into the polymeric membranes at different times. The profiles of liquid concentrations were also simulated for the polymer-solvent systems using the numerical simulation method. Activation parameters for diffusion and sorption were evaluated and these results are discussed in terms of the molecular sizes and geometries of liquids (i.e., shape) as well as temperature. The diffusion coefficients follow a systematic decrease with increasing size of the penetrant molecules. The activation energies i.e., E D values, increase with increasing size of n-alkanes.

RUBBER-SOLVENT INTERACTIONS

Abstract A thorough understanding of the structure physical/mechanical properties of the polymers has made possible the molecular design of macromolecules for specific application needs. Several methods exist for polymer synthesis and processing. When it concerns homopolymers, each polymer structure is identified with a particular method for its realization. Depending upon the situation, one or more of the methods (polycondensation, cationic, anionic, or free radical technique) is sometimes resorted to. Each process has its own merits and demerits. The condensation method is applicable to only a few cases of condensation monomers. A variety of vinyl and cyclic monomers are polymerized by anionic and cationic processes. These processes have obvious disadvantages in the sense that they warrant rigorous polymerization conditions like the need for ultrapure monomers, absolute moisture/oxygen free atmosphere, and cryogenic temperatures which are often difficult to realize on an industrial scale. A recent trend...

INTERACTIONS OF ORGANIC SOLVENTS WITH POLYURETHANE

Abstract Polyurethane elastomers [1] are linear block copolymers of the type in which one of the two blocks is typically a polyether or a polyester diol with a molar mass between 300 to 6000. These blocks comprise the soft segments because at the service temperature they exist in a rubbery or a viscous state and impart elastomeric properties. The other segments are composed of aromatic diisocyanates extended with low diols to produce blocks with molar mass ranging from 500 to 3000. These blocks comprise the hard segments because at the service temperature they exist in the glassy (or semicrystalline) state. Dimensional stability is imparted through microphase separation of the hard segments into domains which act as a reinforcing filler and multifunctional crosslinks. Polyurethanes are mainly thermoplastics because heating above the hard segment glass transition temperature (Tg) will allow the material to flow.

Resistance of barrier elastomers to hazardous organic liquids

Abstract Resistance of barrier elastomers such as ethylene-propylene-diene terpolymer, styrene-butadiene rubber, nitrile-butadiene rubber, neoprene and natural rubber to several hazardous organic liquids has been studied from immersion/dimensional change measurements. Penetration of liquids into these membranes depends on the nature of the barrier material and the liquid molecules. Diffusion coefficients have been calculated for each of the elastomer-solvent systems and their dependencies on concentration have been investigated. Implications concerning the resistivity of elastomer membranes to the presence of hazardous liquids are discussed.

Excess molar volume, excess isentropic compressibility and excess molar refraction of binary mixtures of methyl acetoacetate with benzene, toluene, m-xylene, mesitylene and anisole

Aralaguppi M.I., Aminabhavi T.M. and Balundgi R.H., 1992. Excess molar volume, excess isentropic compressibility and excess molar refraction of binary mixtures of methyl acetoacetate with benzene, toluene, m-xylene, mesitylene and anisole. Fluid Phase Equilibria, 71: 99-112. Excess molar volume, excess isentropic compressibility and excess molar refraction of binary mixtures of methyl acetoacetate (MAA) with benzene, toluene, m-xylene, mesitylene and anisole have been determined. The results are fitted to a third order polynomial relation to estimate the coefficients and standard errors. The excess molar volumes of all the binary mixtures over the temperature range 298.15–308.15 K are positive, suggesting the presence of weak dispersion-type molecular interactions. The isentropic compressibilities are negative for mixtures of MAA with benzene and toluene; however, for mixtures of MAA with mesitylene, anisole and m-xylene, both positive and negative values are obtained. Of all the mixing rules used to predict excess molar refraction, the Eykman relation is recommended for analysis of refractive index data.

Solidification/stabilization study for the disposal of pentachlorophenol

Abstract Solidification/stabilization of toxic pentachlorophenol (PCP) has been studied by using spectroscopic and electrochemical techniques. Portland type I c

An investigation of the long-term sorption kinetics and diffusion anomalies of chloroalkanes into tetrafluoroethylene/propylene copolymer membranes at 30, 45 and 60°C

An investigation of the long-term sorption kinetics and diffusion anomalies of dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene and tetrachloroethylene into the tetrafluoroethylene/propylene copolymer membranes has been carried out using gravimetric sorption technique at 30, 45 and 60°C. Coefficients of diffusion and permeation have been calculated from Ficks equation. Analytical solutions of Ficks equation have been used to compute liquid concentration profiles into polymeric sheet membranes at different times. Activation parameters for diffusion and sorption have been evaluated and these results are discussed in terms of the molecular size of the liquids and the temperature. The diffusion coefficient and activation energy for diffusion do not exhibit any systematic dependence on the size of the penetrant molecules, but these are mainly influenced by the nature of chloroalkanes.

Selective Transport of Oxygen Through Polymer Films—A Review of Literature on Patents

Abstract Over the decade from 1979 to 1989, significant advances have been made towards the study of transport characteristics of commercial polymer films. From a perusal of the literature in this area it is found that more than 400 patents have been published. Of these, about 300 appeared in the Japanese language and the remaining are available in other languages including English. It is, therefore, beyond the scope of any authoritative review to include the full details of all the patents. In this review we attempt to include only the representative data available from the chemical abstracts.